Studies on Lung Volume 



155 



71 (2031) 



Studies on lung volume. V. Quantitative influence of certain 

 factors on admixture. 



By CHRISTEN LUNDSGAARD and KNUD SCHIERBECK. 



[From the Medical Clinic of the University of Copenhagen, Ben- 

 mark.] 



In establishing a complete mixture of air within the lungs 

 with other air several factors come into play. Some of these 

 factors play a minor role and may be varied within rather wide 

 limits before any appreciable influence on the results is observed. 

 Others are of more importance, but their variations can be kept 

 within narrow limits and therefore neglected. There are, how- 

 ever, three factors, which mainly govern the procedure of mix- 

 ing: first, the number of times rebreathing takes place; second, 

 the depth of the respirations; and third, the amount of air left 

 in the lungs after expiration, that is, the amount of air which 

 can be mixed through diffusion only. The methods where 

 mixture is used, or the subjects on whom these methods are ap- 

 plied, often prevent us from choosing the magnitude of these 

 which would be most suitable for obtaining a complete mixture. 

 In a series of experiments, an example of which are reported 

 in this paper, we have investigated the quantitative influence of 

 variations in these three factors. 



Technique. All our experiments are performed on two nor- 

 mal, well trained subjects. We have, for the sake of convenience, 

 exclusively used hydrogen plus oxygen, but earlier experience 

 makes it highly probable that the results can be extended to 

 oxygen, to carbon monoxide, and to nitrous oxide. 



A certain varying amount of hydrogen plus oxygen was intro- 

 duced into a bag or into a Krogh spirometer. The subject 

 started to inspire with a known amount of air left in his lungs. 

 The minimum amount of air left within the lungs was of course 

 the residual air. By starting from different points a known 

 fraction of the reserve air or even of the complimentary air 

 could be added to the residual air. The air left in the lungs was 



